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GRANPECT COMPANY Ltd

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Technical Discussions
Louis Bastarache
Louis Bastarache
02:37 Nov-06-2005
Search unit

Hi everybody,

I just got my new search unit of one inch large but now I need to know if i can check my sound entry point with the IIW block "type one" and if not what should i do?

Thanks


    
 
 
Nigel Armstrong
Engineering, - Specialist services
United Kingdom, Joined Oct 2000, 1094

Nigel Armstrong

Engineering, - Specialist services
United Kingdom,
Joined Oct 2000
1094
01:10 Nov-11-2005
Re: Search unit
Its been a week since you posted, so I hope you managed to check the probe's emission index, Louis.

You do not specify exactly which type of probe you have, but lets say its a 2MHz 1" diameter, 60 deg shearwave. The IIW block (V1) is 25mm thick with a radius of 100mm. This should be ideal for checking the beam emission (index) point. If you are concerned about the probe housing being larger than the block thickness, put two blocks together, they make a 50 mm thcickness..

Best regards

Nigel

----------- Start Original Message -----------
: Hi everybody,
: I just got my new search unit of one inch large but now I need to know if i can check my sound entry point with the IIW block "type one" and if not what should i do?
: Thanks
------------ End Original Message ------------




    
 
 
Udo Schlengermann
Consultant, -
Standards Consulting, Germany, Joined Nov 1998, 176

Udo Schlengermann

Consultant, -
Standards Consulting,
Germany,
Joined Nov 1998
176
01:27 Nov-14-2005
Re: Search unit
reply by Udo Schlengermann:

Two effects cause unacceptable inaccuracies when checking large sized angle-beam-probes on the IIW calibration block (25 mm thick, 100 mm quadrant):

1. side-wall reflections have influence on the pulse shape, i.e. on the maximum echo. So the position of maximum echo amplitude will not necessarily be the one where the beam hits the quadrant surface radially.

2. depending on the frequency the near-field length of a large probe may be larger than the radius of the quadrant (100 mm). Then the maxium echo is disturbed by near-field interferences. So determination of the index point (and beam angle) may be not correct.

Contrary to the reply by Nigel Armstrong, I cannot recommend the use of two parallel 25-mm-blocks, because the interface between the blocks will still cause side wall reflections.

Because of these reasons European Standard EN 12223 on block no 1 allows for modifications (thicker blocks).
European Standard 12668-2 for verfication of probes in annex B for example shows a modification with a thickness of 100 mm.

If your probe has a nearfield in steel larger than 100 mm, you have to use special blocks with a radius larger than that nearfield. Only then the axis of the beam hits the quadrant suface radially at the point of maximum echo amplitude.
Manufacturer's verification has to use blocks with radius up to 200 mm , as required by EN 12668-2.

Kind regards
Udo Schlengermann
Applications Laboratory
GE Inspection Technologies GmbH
Huerth, Germany


----------- Start Original Message -----------
: Hi everybody,
: I just got my new search unit of one inch large but now I need to know if i can check my sound entry point with the IIW block "type one" and if not what should i do?
: Thanks
------------ End Original Message ------------




    
 
 
Nigel Armstrong
Engineering, - Specialist services
United Kingdom, Joined Oct 2000, 1094

Nigel Armstrong

Engineering, - Specialist services
United Kingdom,
Joined Oct 2000
1094
04:12 Nov-15-2005
Re: Search unit
I stand corrected. A practice derived from that usual problem out in the field - lack of resources. Thank you, Udo, for your clear explanation. I shall tell my employers: "Give me the right tools and I shall do my best to give give you a quality result."


    
 
 

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